ML20041B171

Forwards Response to Structural Engineering Branch Request for Addl Info Per 811201-04 Meeting.Use of Elastic Linear Stress Distributions in Analysis of Reactor Bldg Mat Justified

ML20041B171
Person / Time
Site:	Perry
Issue date:	02/16/1982
From:	Davidson D CLEVELAND ELECTRIC ILLUMINATING CO.
To:	Schwencer A Office of Nuclear Reactor Regulation
References
NUDOCS 8202230347
Download: ML20041B171 (7)

Text

e e ill E C L E V E L A N D ELECTRIC  ! L L U in l N AT!!! G C 0 bi P A N Y P o. Box 5000 e CLEVELAND. oHlo 44101 e TELEPHONE (216) 622-9800 e ILLUMINATING BLDG e 55 PUBLIC SoVARE Dalwyn R. Davidson ng e Best Location in IM Nation NST[T[$G$I.itHiNG AND CONSTAUCTION }{p - 9kb UJL.

February 16, 1982 W s_

Cb q Mr. A. Schwencer, Chief SY Licensing Branch No. 2 fEC5iyED D Division of Licensing g U. S. Nuclear Regulatory Commission "l FEB P,219925 g i Washington, D. C. 20555 ,,

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Dear Mr. Schwencer:

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ru As a result of a meeting held with members of the Structural Engineering Branch on December 1 through 4, several action items were identified. The purpose of this letter is to provide responses to an additional set of these action items. Remaining action items will be addressed in future correspondence as agreed upon with the Structural Engineering Branch.

Very Truly Yours,

/s1 dm1 h Dalwyn R. Davidson Vice President System Engineering and Construction DRD: mlb cc: Li Yang John Stefano Jay Silberg, Esq.

Max Gildner, NRC Resident Inspector 90\

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8202230347 820216 PDR ADOCK 05000 A

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ITEM 16 i

Discuss and justify the use of elastic linear stress distributions in the ELAD analysis of the mat. Explain how soil report covering bearing pressures is utilized in the design. Revise p. 21 on RB mat.

Controlling combination for radial rebar Controlling combination for hoop rebar Controlling combination for transverse shear I

Response

The use of elastic linear stress distributions in the analysis of the Reactor Building mat is a very conservative means of analysis, as described in

Section 3.8.5.4.la. Results from this analysis proved quite reasonable so as to preclude a more sophisticated approach.

. Table 4-3 of the PNPP Foundation Design Report, prepared by Woodward-Gardner &

! Associates, lists the allowable contact pressures for the various bearing.

materials. For the Reactor Building mat, which is supported on Chagrin Shale,.

a maximum allowable contact pressure of 25 ksf was used. A 20 percent increase was allowed for short duration loads.

The controlling loading combinations for the radial, hoop, and transverse shear rebar are shown on the attached Analysis / Calculation Sheet.

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ITEM 17 With respect to mat design please provide the following information:  !

4 (a) Results of . LAD analysis at -junction of C.V. shell and mat for 2 load cases: (1) 1.5 P, + D + T, + R, + L (2) 1.0 P, + D + SSE + T, + R, + L (b) Provide integrated section forces and moments at the section defined in 4

(a) above.

(c) Provide the design calculations linking final design forces to rebar areas including radial, hoop, and transverse shear reinforcement.

Response

The ELAD analysis at the junction of the containment vessel and mat is summarized for the two load cases requested. The analysis for all load combinations was performed in two parts with the thermal stresses added only to the critical combination. The thermal stresses for the tao load cases requested are zero (0) in the radial direction and 7.249 kst compression in the tangential direction. The R, term is zero for all load combinations on -

the mat.

. The ELAD results are element stresses which have to be integrated over the section to determine the forces and moments to be used for design.

Load case (1) 1.5 P, + D + T, + R, + L is defined in the calculations on pages 3:06.2-3.59 to -3.63 with the addition of the hydrostatic load G. Load-case (2) 1.0 P, + D + SSE + T, + R, + L is defined in the calculations on pages 3:06.2-3.66 to -3.67 with the addition of the hydrostatic load G. The-following table summarizes the results.

Item 17 (page 2) continued:

Quantity Load Case 1 Load Case 2 M (radial) (in.-k/in.) 479.3 -1300.0 M (tangential) (in.-k/in.) 167.2 -883.0 F (radial) (k/in.) -1.178 F (tangential) (k/in.) -0.9988 *

-4.776

• V (vertical) (k/in.)

• Not tabulated in original calculations because load combination was not critical.

The design calculations (3:06.2-5.2 to -5.38) linking final design forces to rebar arear are attached.

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ITEM 18 Justify basis for not providing a vertical and tangential earthquake restraint for the polar crane for both the loaded and unloaded condition.

Response

4 The polar crane bridge is provided with lateral and longitudinal seismic restraints to prevent rossible crane derailment during postulated seismic and SRVD conditions. Vertical seismic restraints are not required for the crane i

bridge since the maximum dynamic reactions do not exceed the minimum dead load reactions at the ends of the crane bridge.

i The table below lists the minimum factors of safety for various trolley i locations and dynamic events. Conservatively, the crane is considered unloaded, and maximum dynamic reactions are ratioed with minimum dead load reactions even though they do not occur at the same location when the factors i of safety are calculated.

The crane trolley is proviaed with both horizontal and vertical restraints.

BRIDGE UPLIFT FACTORS OF SAFETY

, FOR UNLOADED CRANE, COMBINED SRVD & SEISMIC LOADS-Loading Trolley Location -Factor of Safety

• l' SRV + OBE Center Span 2.0 (OBBA) 1/4 Span 1.2 End Span 1.2

! SRV + SSE Center Span 1.5 (SSBA) 1/4 Span 1.1 End Span 1.3

• Factor of Safety

, Minimum Static Load Maximum Dynamic Load l

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Item 18 (page 2) continued DYNAMIC REACTIONS (KIPS)

(NOT INCLUDING DEAD LOAD)

Trolley OBE + SRV SSE + SRV Location V V v v 7 2 i 2 Center 19.3 16.3 25.1 20.7 1/4 Span 35.5 30.6 39.8 31.7 End Span 38.7 31.4 36.4 30 3 I

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c STATIC CRANE WilEEL LOADS U

OBE HSE $-

V' V 11 11 ' II .V V 11 11 11 -

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1 2 1 2 3 1 2 1 2 3 oc,

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, ~ Trolley @ Center 72.8 67.9 ' - - -

72.8 67.9 - - -

of Span u Trolley @ Quarter 93.9 89'.6 .- - -

93.9 ' 89.6 - - -

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Point of Span Er r

Trolley @ End 110.2 106.3 - - -

110.2 106.3 - - -

4 of Span OBBA (OBE + SRV) SSBA (SSE + SRV)

V V ii H II "1-3 2 l 2- 3- ' 1 2 2 ' 3 i

Trolley @ Center 42.[ 37.9 - - -

42.3 37.9 - - -

J .. of Span K

Trolley @ Quarter 46.8 43.0 -- - -

46.8" 43.0 - - -

Point. of Span K

Trolley @ Fnd 46.9

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50.3 46.9 - - -

50.3 - - -

'. of Span 1

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ITEM 19 Please provide design cases assessing 2 structures (shield building and drywell) for the load combination including 1.7 R, as presented in the FSAR

p. 3.8-111a item 9.3. Please provide a statement of justification for each deviation from ACI-349-76 as modified by Reg. Guide 1.142 (April 1978) for all Category I structures.

Response

Load combinations including 1.7 R are summarized on the following pages and 9

include load combinations 2 and 10 of ACI 349 as modified by Reg. Guide 1.142.

Because these tre factored (load factors greater than 1.0) load combinations, they do not address accident conditions nor the design of the steel embedment.

Rather, they only involve checking the various concrete capacities such as shear and flexure in the local pipe penetration region. Because of the high pipe rupture forces generally associated with penetration anchors in shield building and drywell type structures, these load combinations usually do not govern.

Also, the R term is defined as pipe reactions during normal operating or shutdown conditions based on the most critical transient or steady state conditions, and is primarily limited to process pipe thermal reactions.

Seismic reactions due to the process pipe use the more conservative 1.9 load factor. Reactions due to SRV vibrations use a 1.7 load factor, which is i higher than the more generally accepted factor of 1.5 for this load. This conservatism alone would bound the difference in the 1.7 and 1.3 factors used on R .

o As'shown on a following page, ACI 349 load case 10 is bounded by our desig".

normal operating load case. The only differences between our design Ic.;d case and ACI 349 load case 2 is that our load case used 1.3 R instead of 1.7 R o o and our load case also included overall thermal considerations of 1.3 T,.

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Item 19 (page 2) continued To help demonstrate the minor effect on our design the increase in loads due to the chanc- from 1.3 Ro to 1.7 Ro tables showing the change in reactions have .en provided. These small increases in reactions plus the observation, presented above clearly demonstrate the conservatism of our designs end load combinations.

A statement of juttification has been added for each deviation from ACI 349-76 as modified by Reg. Guide 1.142 (April,1978) for all Category I structures in the response to revised SEB question 220.16 attached.

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. 220.16 With reference to FSAR Section 3.8.1.2, 3.8.3.2, 3.8.4.2 and (3.8.1, 3.8.5.2, applicable codes, standards and specifications, 3.8.3 it is the staff's position that ACI 349-76 Code should be 3.8.4 and used in conjunction with Regulatory Guide (R.G.) 1.142, 3.8.5 Identify deviations of Category I structural design from the requirements of the code and the Regulatory Guide and justify your deviations.

Response

The extent of compliance to ACI 349-76 is given in Section 3.8.3.3.7. A new Section 3.8.1.3.7 has been added to reference this Section. Section 3.8.4.3.3 also references Section 3.8.3.3.7.

Our compliance to Regulatory Guide 1.142 has been added in revised FSAR Sections 3.8.1.2.2, 3.8.3.2.3, 3.8.4.2.2, and 3.8.5.2.2.

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4. Regulatory Guide 1.142 (April,1978), " Safety-Related Concrete Structures For Nuclear Power Plants (Other Than Reactor Vessels and Containments)." We generally comply with this guide except the 0.9 load factor for dead load was not used as required by Item 11. We j have assessed this reduced load factor on several key structures

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including the Drywell, Reactor Building foundation mat, the Auxiliary A Building roof slab, and the Fuel Handling Building roof slab. Our evaluations demonstrate that we meet the intent of this Regulatory Guide requirement.

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3.8.1.3.7 Extent of Compliance to ACI 349-76 " Code Requirements for Nuclear s O'

Safety Related Concrete Structures", American Concrete Institute. o'

'Y The extent of compliance to ACI 349-76 is discussed in Section 3.8.3.3.7.

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3.8-16a

4. Steel Plate: Section 3.8.2.7.1 and 3.8.1.6.4.

5. Structural Steel: Section 3.8.3.6.5.

6. Stainless Steel: Section 3.8.3.6.6.

3.8.3.2.3 Applicable Regulatory Guides to Design Regulatory guides pertaining to seismic design classification and seisaic design are referenced in Sections 3.2 and 3.7, respectively.

1. Regulatory Guide 1.10, " Mechanical (Cadweld) Splices in Reinforcing Bars of Seismic Category I Concrete Structures". This guide was used with modifications specified in Section 3.8.1.6.3.

2. Regulatory Guide 1.15, " Testing of Reinforcing Bars for Category I Concrete Structures", This guide was used with modifications as set forth in Section 3.8.1.6.2.

3. Regulatory Guide 1.31, " Control of Stainless Steel Welding".

4. Regulatory Guide 1.55, " Concrete Placement in Category I Structures."

5. Regulatory Guide 1.57, " Design Limits and Loading Combinations for Metal Primary Reactor Containment System Components".

6. Regulatory Guide 1.69, " Concrete Radiation Shields for Nuclear Power Plants."

7. Regulatory Guide 1.71, " Welder Qualification for Areas of Limited Accessibility".

8. Regulat ory Guide 1.142 (April, 1978), " Safety-Related Concrete Structures '$.

For Nuclear Power Plants (Other Than Reactor Vessels and Containments)". a Also see Section 3.8.1.2.2.b.4. 6 3.8-105

3.8.3.3.4 Load Combinations for Local Areas The load factors used for the design of local areas are the same as those used for the general structure and outlined in Sections 3.8.3.3.2 and 3.8.3.3.3.

3.8.3.3.5 Time Dependent Effects Prestressing is not included in the design for any part of the interior structure and therefore the effects of time dependent variations in loads are not of a significant nature.

3.8.3.3.6 Thermal Effects Temperature profiles have been calculated for the various pertinent operational conditions of the plant using the method discussed in Section 3.8.1.4.3.a.4 and are shown in Figure 3.8-38 through 3.8-41 for typical sections.

3.8.3.3.7 Extent of Compliance to ACI 349-76

" Code Requirements for Nuclear Safety Related Concrete Structures", American Concrete Institute ACI 318-71 which was used for concrete structures on the PNPP and ACI 349-76 are quite similar. For this reason, PNPP is, in general, in compliance with the requirements of ACI 349-76. Specific sections where ACI 349 differs from ACI 318 and PNPP compliance to these items are summarized below:

Paragraph 6.3.3 Limits concrete temperatures to 150 /200 F for normal operating conditions and 350 /650 F for accident conditions. PNPP is in compliance. Reference to Sections 3.8.1.4.5.c and 3.8.3.4.4.c.

6.4 Requires engineer approval of all construction joints not shown on l the drawings. PNPP requires engineer approval of all construction 4

joints not shown on the engineers' drawings in the concrete  ?-

placement specification. PNPP is in compliance.

3.8-111

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7.3.2 ACI 301 reinforcement placement tolerances are adopted by ACI'349.

Rebar placement tolerances for PNPP are as described in Sections 3.8.1.6.2.4 and 3.8.3.6.2. Where deviations from ACI 301 exist,-

justification is provided in these sections.

7.5.5 Specifies staggerErequirements of 36-inch minimum for mechanical splices which do not meet specified strain requirements. A 3'-0" stagger was used for adjacent cadweld splices in the drywell-structure. A 2'-0" stagger was specified for adjacent cadwelds for the No. 11 horizontal reinforcement in the weir walls. At certain construction opetings where adjacent bars were cadwelded no stagger was provided. The use of mechanical splices was minimal except for the drywell structure and weir wall as-discussed above.

The concern of the code was that at unstaggered mechanical splices, a crack'could develop which would permit additional member rotations with a reduction in member capacity. Tests in 4 beams have demonstrated this. The examples cited above are not ,

o subject to this concern. The cylindrical shape of the weir would ,

preclude such a condition by geometry considerations alone. The -

construction openings in walls are relatively small and generally subjected to membrane loads rather than the flexural loadings of a beam.

7.5.6 Requires tests acceptable to the NRC on welded' splices and positive connections. Such tests have been provided on PNPP as described in Section 3.8.1.6.3. PNPP is in compliance.

7.6.4 Requires mechanical splices in biaxial tension regions. In structures such as the drywell cylindrical wall and top slab where large areas of biaxial tension exist, mechanical cadweld splices have been used. PNPP is in compliance.

3.8-111a

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1 7.13 Specifies minimum shrinkage and temperature reinforcement ratios of reinforcement-area to' gross concrete area.- Reinforcement -

ratios provided for PNPP exceed the minimum requirements of ACI1349. PNPP is in compliance.

, Chapter 8 -Deletes reference to the " Alternate Design Method". The alternate

! design method was not used on PNPP. PNPP is in compliance.

9.3 Specifies that.the required strength U shall at least equal:the strengths required by the specified load combinations.

The load combinations as specified in Sections 3.8.1.3.2, 3.8.3.3.. 2 , 3.8.4.3.2, and 3.8.5.3 meet or exceed the requirements of ACI 349. Only the load factor of 1.7 specified for R exceeds o

the 1.3 factor used for the same term on PNPP. This is not a controlling case, however, because on PNPP thermal has been-combined with R, and because of the higher factor used on the steam relief valve reactions. We have assessed this increased q load factor on several key structures including the shield 4

building (feed water penetration anchors) ~and the drywell (main J l steam penetration anchors). Our evaluations demonstrate that we d

meet the intent of ACI 349 as modified by Reg. Guide 1.142.

I 9.5 Minimum thicknesses of beams and one-way slabs required by ACI. 349

! are somewhat greater than ACI 318 requirements. Because'most of the slab thicknesses used on PNPP are determined by shielding '

requirements, slab thicknesses generally exceed the ree_uirements for specified spans and support conditions. Prestressed concrete j was not used on the PNPP. PNPP Is in compliance.

3.8-111b c.-., , . . . . ,, -_ . , _ , , . -- _ - - - , . .. ., . - . . -

3.8.3.4 Design and Analvsis Procedures 3.8.3.4.1 Design Assumptions and Boundary Conditions

a. Drywell Wall, Top Slab, and Fuel Pool Walls Several finite element models are used to analyze the drywell structure.

The first model is a three dimensional finite element model used for the overall analysis of the drywell. It' encompasses the drywell wall, drywell top slab, refueling pools and major sub-compartments. Because of symmetry of loadings and structure, only half of the drywell is modeled as shown in Figure 3.8-42. The vent region is idealized by quadrilateral sandwich plate elements which consist of a concrete core lined on both sides by equal thickness steel face plates. Both the concrete core and the face plates are assumed to be linearly elastic, homogeneous, isotropic materials. Vent holes are not modeled, but their effects are fully accounted for by the method of reduced elasticities as discussed in Section 3.8.3.4.2.- The reinforced concrete section of the drywell . wall, the top slab, the refueling 3.8-111c

The date of a particular standard may vary for different items because of the difficulty in purchasing material to an outdated standard. Since the latest ASTM standards reflect industry practice used for fabrication and erecti sn, it was permitted to use an updated standard where no unacceptable loss of quality would result.

b. Applicable Regulatory Guides

1. Regulatory Guide 1.10, " Mechanical (Cadweld) Splices in Reinforcing Bars of Category I Concrete Structures". This guide was used with modifications specified in Section 3.8.1.6.

2. Regulatory Guide 1.15, " Testing of Reinforcing Bars for Category I Concrete Structures". This standard was used with the modifications specified in Section 3.8.1.2.

3. Regulatory Guide 1.31, " Control of Stainless Steel Welding".

4. Regulatory Guide 1.55, " Concrete Placement in Category I Structures".

5. Regulatory Guide 1.69, " Concrete Radiation Shields for Nuclear Power Plants."

6. Regulatory Guide 1.142 (April, 1978), " Safety-Related Concrete Structures For Nuclear Power Plants (Other Than Reactor Vessels and Y .

Containments)". Also see Section 3.8.1.2.2.b.4. .}

s 3.8.4.2.3 Principal Plant Specifications The principal specifications prepared by the engineer for the safety class structures are:

a. Fabrication and erection of structural steel.

3.8-148

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b. Applicable Regulatory Guides Regulatory guides pertaining to seismic design' classification and seismic design are referenced'in Sections 3.2 and 3.7, respectively.

1. Regulatory Guide 1.10 " Mechanical (Cadweld) Sprices in Reinforcing Bars of' Category I Concrete Structures". This standard was used with modifications specified in Section 3.8.1.6.3.

2. Regulatory Guide 1.15 " Testing of Reinforcing Bars for Category I Concrete Structures". This standard was used with the modifications specified in Section 3.8.1.6.2.

3. Regulatory Guide 1.55, " Concrete Placement in Category I Structures."

4. Regulatory Guide 1.142 (April, 1978), " Safety-Related Concrete ,

'I Structures for Nuclear Power Plants (Other Than Reactor Vessels and Containments)". Also see Section 3.8.1.2.2.b.4. f.

.h 3.8.5.2.3- Principal Plant Specifications The principal specifications prepared by the engineer for the foundation' structures are: -

a. Concrete supply,

b. Placement of structural concrete.

c. Fabrication and placing or reinforcing steel.

d. Plant excavation and-backfill.

e. Fabrication of embedded steel.

f. Supply and installation of waterproofing and waterstops.

3.8-200

ITEM 20 Evaluate and justify the design of. duct banks at the building structure considering the combined moment and shear effects of differential displacements and free field shear wave motions. Please check one section.

Conclusion:

The results of our evaluations demonstrate the adequacy and conservatism of our designs.

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_I_TEMS 22'AND 38 ITEM 22 (a) Explain omission of tornado missiles in' load combinations of diesel generator building for overall response.

(b) ~ Verify compliance with load combination equations for tornado loads of~SRP 3.3.2 and explain inclusion of these loads in design of other Category I structures.

ITEM 38 Please provide supporting calculations for overall response due to missiles for key Category I structures as presented in your response to question 220.07.

Response

The-design for tornado missiles on the Perry project was considered in general for all. structures. A study of the literature was made (see' attached reference list) to establish a design procedure to be used on all Seismic Category I structures. Attention was given to experimental studies (References ~4,' 5, 7).

which confirmed that test missiles impacting 24 inch thick concrete' panels neither penetrated nor caused structural failure. The basic outcome of this investigation is stated in the FSAR 3.5.3: "The exposed. walls and roofs lof Seismic Category I structures have a minimum concrete thickness of 24 inches and are reinforced each way on each face with a minimum of No. 8 bars at 12-inch center-to-center for walls and No. 9 bars at 12-inch center-to-center

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for slabs. ' Typical elements were evaluated for local effects of penetration, perforation, and scabbing as well as overall structural response."

The typical elements mentioned above were taken from the Auxiliary Building, Control Complex and Radwaste Building. .There typical elements were beams, columns, walls and roof slabs. In each case the element met basic requirements for safety. The design calculations for the Radwaste and Control Complex Buildings are attached.

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ITEMS 22 AND 38 (Page 2) Continued Based on *he literature study and the calculations presented, it was determined that tornado missile protection could be adequately achieved using the 24 inch thickness with minimum steel as defined in the FSAR statement.

ITEM 27 Specify the sample population (no. of mill certs) used to determine the material properties for the ultimate capacity analysis and the confidence level for the lower and mean values of the yield stress used in the design of the containment.

Response

The sample population for the containment vessel material properties is:

Unit 1 Dome - 120 (120 total plates)

Unit 1 & 2 Cylinder - 306 (312 total plates)

The lower bound material properties are defined as the mean value minus three standard deviations.

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ITEM 39 Please confirm that Appendix A to SRP Section 3.5.3 regarding ductilities for

<- structural elements under biaxial tensile stresses is met with regard to your drywell design. If a deviation to this position exists provide justification by discussing its inherent safety margin.

- Response i

Appendix A to SRP Section 3.5.3. addresses ductility ratios for reinforced-concrete and steel structural elements subjected to impactive and impulsive loads,.such as impacts dur to missiles. Regarding Appendix A, the drywell design does comply with the requirements of this staff position in the drywell 1

design.

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-ITEM 43-4 In the FSAR Section 3.7.3, you stated that equipment supported at different locations-is analyzed by-imposing single conservative response spectrum at- ,

each location. This response spectrum is considered in such a way that it

- conservatively envelopes the pertinent response spectra. Please provide a ,

specli example of how the stated conservatism in the analysis is achieved.

Also please indicate your compliance with the acceptance criteria of SRP Section 3.7.3.II.2.i.

Response

There are two way that response spectra are used in piping analysis where components such as piping are supported at several points by either a single structure. or two separate structures. These - two methods are described below J

and are in compliance with the acceptance criteria of SRP Section 3.7.3.II.2.i. Relative support displacements are considered on the supported item in the most unfavorable combination. ~The responses due to the 4

inertia eff ect and relative displacements are combined by'the absolute sum

, method.

I. Enveloped Response Spectrum Since our PIPDYN computer program can consider only one response spectra curve at a time, all the possible response spectra curves that can'be applicable on a given piping run are plotted on one curve. The envelope of this plot is then used in the analysis. This procedure is-followed for the "x" direction, "y" direction, and "z" direction.

An example of this is shown on page 3. The response spectra for a given direction are:

(1) 1st enveloped for the given building by elevations. Elevation 1 and 2 are enveloped.

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-+&-- .-u+5, 3 m 7-y -ma w .w , _

,_,q_e__ _

,,m9 wm5 g- p ,,y 1 -- ,--rM- +=$--*-7-'*w--ew-m -y '

y=-

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- Item 43 (page 2) continued (2) The enveloped curves for each- building are 'then again enveloped to combine' buildings.

The conservatism in this approach is evident.

II. Multi-Response Spectra Multi-Response Spectra is used only with computer programs which can

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treat one or more response spectra for a given direction. The example shown on page 3 would be treated as follows: ,

1) The envelope of the two elevations for each building are generated.

2) The envelope of Elevations 1 and-2 of Building 1 would

.i be defined as Zone 1 and the envelope of Elevations 1 and 2 of Building 2 would be defined as Zone 2.

, 3) The computer- program would then execute the response spectra j analysis accounting for each of the zones and their-i interaction.

l While this approach is relatively new, it has wide industry use and is considered to be a conservative approach.

Item 43 (page 3) continued o

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ENVELOPE OF ELEVATIONS 1 AND 2 ENVELOPE OF E8.EVATIONS 1 AND 2 BUILDING 1 BUILDING 2 b b 5 5 d d 0

4 0

FREQUENCY FREQUENCY BUILDING 1 BUILDING 2 ELEVATION 2 s

5 ELEVATION 1 fr rrrrr r rrrrrri rr

1. EXAMPLE OF ENVELOPE APPROACH ENVELOPE CURVE OF BUILDING 1 AND BUILDING 2 l

11. MULTI-RESPONSE SPECTRA A. BUILDING 1 ENVELOPE IS USED AS ZONE 1.

B. BUILDING 2 ENVELOPE IS USED AS ZONE 2.

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